1. Field of the Invention
The present invention relates to a three-dimensional measurement method in which a non-contact three-dimensional measurement device such as an optical three-dimensional measurement device is used to conduct measurement of a surface shape of an object and a system for the three-dimensional measurement method. The present invention also relates to a method and device for controlling a manipulator.
2. Description of the Related Art
For the purpose of visual inspection of an object, an optical three-dimensional measurement device for light-section method has been used to conduct measurement of a surface shape (a three-dimensional shape) of the object. At the time of such measurement, any one of the object and the three-dimensional measurement device is fixed and the other is held by a multijoint manipulator, for example, a robot arm. Then, the manipulator is controlled to change relative positions and postures of the object and the three-dimension measurement device (U.S. Pat. No. 6,970,802).
As shown in FIG. 10, for example, a three-dimensional measurement device VD is placed on the floor FL. An object Q is held by a manipulator MP through a jig JG to determine a position and posture of the object Q. The manipulator MP is controlled to change the position and posture of the object Q variously, so that the three-dimensional measurement device measures the entire circumference of the object Q. The manipulator MP can rotate relatively at joints KS1-KS3. In the case where the object Q is, for example, in the process of development or a prototype for mass production in factories, the same measurement is repeated for the objects Q having the same shape. Accordingly, it is necessary to teach a manipulator all positions and postures for the measurement.
Conventionally, in the case of the teaching for a manipulator, an operator moves the manipulator MP by manual operation to determine a position and posture of an object Q for conducting measurement. If the result shows that the measurement is undesirable, the operator operates the manipulator MP again to change the position and posture of the object Q. After repeating this operation, an appropriate position and posture of the object Q is determined after trial and error.
The trial and error method as described above, however, involves lots of time and energy for determining a position and posture of a three-dimensional measurement device.
Suppose, for example, that after conducting measurement under the state as shown by the solid line of FIG. 10, in order to measure a recess portion B of the object Q, it is intended to change the posture of the object Q so that the bottom of the recess portion B faces the front of the three-dimensional measurement device VD. In such a case, suppose that the joint KS1 is rotated to incline the object Q so that the front face of the object Q faces downward and the posture of the object Q is changed, as shown by the chain line in FIG. 10. This allows the bottom of the recess portion B to face the front. However, the posture change causes the position change, so that the recess portion B is out of a measurable area KR of the three-dimensional measurement device VD. Measurement is impossible under such a situation. Accordingly, it is necessary to finely adjust rotation directions and rotation angles of the plural joints KS1-KS4 of the manipulator MP so that the recess portion B faces the front of the three-dimensional measurement device VD and falls within the measurable area KR. Such fine adjustment requires much time.
In order to conduct measurement of the entire surface of an object, measurement is generally necessary at least at five positions. In some cases, measurement is conducted at twenty positions or so. As a surface shape of an object becomes complicated, longer time is required to determine a position and posture for measurement of a portion of the surface shape.